Stable-Carbon Isotope Variability in Tree Foliage and Wood

This study documents variation of stable—carbon isotope ratios (13C/12C) in trees of genera Juniperus and Pinus under field conditions. Results are from cellulose analysis on leaves, twigs, and wood from a number of localities in the southwestern United States. Substantial variability, typically 1—3@%, exists among leaves, within wood (radially, vertically, circumferentially), and between individuals at a site. These results may help guide sampling in tracer—type studies with stable—carbon isotope ratios and aid in the interpretation of isotopic results from such studies.